Push-in spinal fusion implants (allowing for the growth of bone from adjacent vertebral body to adjacent vertebral body through the implant) having upper and lower surfaces adapted for placement by linear insertion within a disc space and in contact with the adjacent vertebral bodies are known in the related art. Such a push-in spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,776,199, filed Jun. 28, 1988, which is hereby incorporated by reference. Push-in spinal fusion implants offer the advantage of being easily positioned in the implantation space and of having the ability to have varying height to width ratios.
Lordotic or tapered, push-in spinal fusion implants are also known in the art. By way of example, Michelson has invented such implants as disclosed in U.S. Pat. No. 5,609,635, filed Jun. 7, 1995, which is hereby incorporated by reference. Lordotic or tapered, spinal fusion implants may more easily restore or enhance spinal lordosis.
Spinal fusion implants having projections that can be deployed after the implant has been inserted into the disc space are also known in the related art. An example of a spinal fusion implant having deployable projections was invented by Michelson and also is disclosed in U.S. Pat. No. 5,776,199 previously incorporated by reference herein. Other examples of implants having deployable projections include, but are not limited to, U.S. Pat. No. 6,179,873 to Zientek and International Publication No. WO 01/01894 A1 to Bolger et al. Examples of spinal fusion implants having rotatable elements for fixing the implant to the vertebrae include U.S. Pat. No. 6,210,442 to Wing et al., U.S. Pat. No. 6,090,143 to Meriwether et al., and U.S. Pat. No. 5,888,228 to Knothe et al.
None of the related art implants have a rotatable internal member with bone engaging projections that are retracted within the interior of the implant to permit the implant to be inserted into the disc space and then deployed to extend through the exterior of the implant to penetrably engage the adjacent vertebral bodies, while permitting bone growth from adjacent vertebral body to adjacent vertebral body through the interior of the implant and the interior of the internal rotatable member substantially unimpeded by the internal rotatable member and bone engaging projections.
There exists a need for a spinal fusion implant providing for all of the aforementioned features in combination.